It has previously been proposed to create horizontal or vertical voids in oil shale and to fragment adjacent oil shale into these voids, and subsequently ignite the rubblized shale. Under limited combustion conditions, combustible product gases and oil resulting from decomposition of the organic kerogen contained in the oil shale is obtained in accordance with known techniques. This is known as modified in situ oil shale retorting.
The composition of oil shale may include calcium magnesium carbonite or dolomite, and the organic kerogen material. In relative lean oil shale, of the type which produces less than about 25 or 30 to 35 gallons of oil per ton of oil shale, the inorganic material is phase continuous and the kerogen material is isolated throughout the shale. This lean shale is relatively incompressible even at high temperatures. In the richer oil shale, however, the kerogen is phase continuous and the calcium magnesium carbonate molecules are spaced through the organic material.
In modified in situ oil shale operations, this richer oil shale has caused some problems. More specifically, with the organic material predominating, the rich oil shale, when heated, is compressible, and tends to flow and compact, with the effect of blocking the desired flow of air and other gases, and liquids, through the rubblized oil shale.
A principal object of the present invention is to avoid this undesired compression of the oil rich shale and the resultant blocking of the gas and liquid flow.